A unit of the type of the species is already known in which the character elements are made in the form of fingers supported movably in the table perpendicularly to the plane of the table, which fingers are movable between a set position projecting out of the table place and a cleared position retracted into the plane of the table by means of pistons which are arranged on the side faces of the table and are respectively movable perpendicularly to the direction of motion of the fingers (German Offenlegungschrift No. 2,848,852). The operating pistons are made in the form of plungers which are respectively movable by magnet coils. The extremely expensive construction in which the operating pistons are arranged perpendicularly to the direction of motion of the fingers was chosen in order to be able to hold the fingers firmly in their set position by mechanical means without any holding current having to flow in the magnet coil for example. This has the result that each operating piston must have assigned to it either two separate magnet coils or one magnet coil operable in two effective directions for the setting and clearing of the fingers. The operating pistons arranged perpendicularly to the direction of motion of the fingers occupy a very large mounting space, so that for this reason alone any multi-line coverage of a reading table is not possible in practice. Besides this, in a general way in the known construction the expense for actuating means, operating means and the high electrical output required for operating the magnets is very disadvantageous, so that for this reason too only a comparatively small number of character fields can ever be combined on one reading table; in the case of the known construction as many charcter fields were chosen as were necessary for the display of one line of type of a computer viewing screen unit. The reproduction of multi-line texts, columns of figures, tables or large-area graphic patterns is not possible with character elements of the known type at a justifiable cost.